Not Applicable
Not Applicable
1. Field of the Invention
This invention relates to wireless communication service networks, including networks servicing cellular telephones, personal communication systems, and the like. More particularly, the invention concerns a wireless message processing system and the control of message processing resources therein in response to a processor shutdown condition.
2. Description of the Prior Art
Wireless communication service networks employ message processing systems that provide operational, administrative and maintenance functionality in support of cell base stations that communicate with wireless radio units. When a call is originated from, or terminated to, a wireless radio unit located in a cell managed by a cell base station, the message processing system serving the base station routes signaling messages that enable the base station to perform the necessary call set-up, knock-down, hand-off and paging functions. Message processing support may also be implemented for subscriber-specific intelligent network services, such as Call Forwarding, Call Waiting, Three-way Calling, Calling Line Identification and the like.
Existing message processing systems are implemented using programmed computers. These are referred to by various names, including Application Processors (APs), Base Station Controllers (BSC) and the like. For convenience, the terms xe2x80x9cApplication Processorxe2x80x9d and xe2x80x9cAPxe2x80x9d will sometimes be used hereinafter to refer to components of the message processing system described herein. It will be understood that the use of such terms is not intended to signify any particular architecture or commercial product offering.
Overload in a network message processing system can occur as a result of excessive message traffic and over-demand for system functions. This can cause messaging delays and lower quality of service to wireless subscribers. As such, conventional message processing systems typically implement OverLoad Control (OLC) functionality, whereby message processing is throttled (e.g., messages are dropped) if system usage exceeds a predetermined OLC threshold relative to some operational benchmark. A typical benchmark is CPU utilization, and a CPU utilization rate of 80% is sometimes used as the OLC threshold. When an AP in a message processing system reaches this threshold, message throttling is invoked, and continues until the AP is out of the overload condition.
In some wireless communication service networks, such as the FLEXENT(trademark) system from Lucent Technologies Inc., message processing and other network functions are implemented on behalf of cell base stations by clusters of APs arranged in a networked environment. In the event that one AP shuts down (e.g., it fails unexpectedly or is intentionally taken out of service), the AP""s message processing functions can be off-loaded to other APs. Although this procedure may work satisfactorily in an environment where overall CPU utilization is low, it can fail if CPU utilization is already at or near the OLC threshold for the other APs. For example, if CPU utilization is already at 75% for all APs in a system that uses an 80% OLC threshold, there may not be enough excess capacity to take up the messaging load from the non-operating AP. Using a single OLC threshold for all APs in a cluster thus may not provide effective overload control in the event of an AP shutdown. Effective message processing cannot occur if the remaining APs, although not overloaded, do not have spare capacity to take up the messaging load from the non-operating AP.
Accordingly, there is a need in a wireless communication service network, and particularly a network implementing clustered APs, for improved control of message processing resources in response to an AP shutdown condition. What is required is a message control system that is dynamically responsive to an AP shutdown condition in order to promote improved load sharing among remaining operational APs and to minimize the likelihood of a catastrophic processing failure.
A solution to the foregoing problem is provided in a wireless communication service network that includes a message processing system with at least two programmable application processors (APs) providing operational, administrative and maintenance support for one or more cell base stations in the network serving one or more wireless radio units. Improved control of AP message processing resources is provided in response to an AP shutdown condition. In accordance with the improvement, an initial AP OLC threshold is set for the APs, and the APs are monitored during their operation as they perform message processing. In the event that one of the APs becomes non-operational (non-operating AP), the OLC threshold relative to remaining operational APs is dynamically increased. The message processing functions of the non-operating AP are then redistributed to the operational APs.
The foregoing functions can be implemented by software or firmware programming in a control processor that monitors and directs the activities of the APs, or by programming in the APs themselves. The initial OLC threshold is preferably selected at a level that allows sufficient upward threshold adjustment to enable all remaining operational APs in the message processing system to absorb the message processing functions of the non-operating AP. This initial OLC threshold can be determined by performance modeling or by observation of the wireless communication service network during actual or simulated operations with and without a non-operating AP in place. More particularly, the initial threshold can be determined on the basis of processor utilization and message delay considerations with all APs being operational, and following the shut down of an AP with the remaining operational APs carrying an increased load.
The APs may either be paired or unpaired. If the APs are paired, the OLC threshold adjustment following an AP shutdown is performed by adjusting the OLC threshold for the paired mate of the non-operating AP. The message processing functions of the non-operating AP are then redistributed to the mate AP. If the APs are not paired, the OLC threshold adjustment following an AP shutdown is performed by adjusting the OLC threshold for some, and preferably all, of the remaining operational APs in the message processing system or in an AP cluster therein. The processor functions of the non-operating AP are then be distributed to at least some, and preferably all, of the remaining operational APs.